This invention relates to a heat exchange installation.
In heat exchange installations there are provided a heating system, a pump, more particularly a circulating pump, for the forced conveyance of a heat-carrying medium, for example oil, or other pumpable substance, under defined conditions of flow. An expansion vessel and a storage vessel for the heat-carrying medium or the other pumpable substance are also provided. When the heat-carrying media and any other pumpable substances are temperature-controlled and maintained in circulation under predetermined conditions of flow or otherwise further conveyed, it is necessary, for example in the case of heating installations, for a heat-consuming unit to be maintained at a predetermined temperature by means of the heat-carrying medium. For safety reasons, a film temperature increase at the tube wall must be maintained within closely defined limits in order to avoid thermal decomposition of the heat carrier. This is made possible by a forced circulation of the heat carrier under defined conditions of flow.
Heat exchange installations are known, in which the heat transmission is effected by:
(a) free convection (natural circulation, thermosyphon); PA1 (b) natural convection; and PA1 (c) forced convection.
While substantially only water is used as the heat-carrying medium in heating installations according to (a) and (b), various heat-carrying media may be employed in heating installations according to c). More particularly, such installations are suitable for the use of oil as the heat-carrying medium, because the danger of thermal decomposition of the oil is low.
Two types of such installations are known.
One type is an "immersion heater" system, in which the heat-carrying medium is heated in a storage container by means of electrical heating elements and is maintained in circulation by a circulating pump. In this case, the disadvantage exists that, owing to the lack of a defined or regulated flow in the heating system, an uncontrolled thermal loading of the heat-carrying medium may occur, which may result in thermal decomposition and hence cause fire and safety problems when oil is employed as the heat-carrying medium. (In Germany, for example, it is no longer permitted to install new heat exchange systems of this kind for the use of oil as heat carrier.) On the other hand, however, sealing to prevent leakages of heat carrier can be more readily carried out in such immersion heater systems.
The second kind of heat exchange installation comprises a forced-circulation heater. In this case, the heat-carrying medium is maintained in forced circulation under defined or regulated conditions of flow. With simultaneous heating of the heat carrier, a known heat flux density is ensured, so that there are substantially no difficulties with regard to the possible thermal decomposition of the heat-carrying medium, for example heat-carrying oil, in contrast to the case in the immersion heater system. On the other hand, in heating installations or apparatus having forced flow which are known to me, in Germany, a large number of connecting flanges with sealing points is necessary, so that there is a large number of possible leakage points. For this reason, inter alia, such forced-circulation installations involve higher cost of labour and equipment than immersion heater systems.